setting version to 0.9.28-rc1

Signed-off-by: Michael Kaufmann (d00p) <d00p@froxlor.org>
fix idna conversion for UTF-8, thx to anbrosius (via github)

Signed-off-by: Michael Kaufmann (d00p) <d00p@froxlor.org>
fix and cleanup polish language file, thx to imachine; fixes #1170 refs #1171

Signed-off-by: Michael Kaufmann (d00p) <d00p@froxlor.org>